First-Principles Study of Hole-Doped Superconductors RNiO₂ (R = Nd, La, and Pr)

Recent experiments have found that in contrast to the nonsuperconducting bulk RNiO2 (R = Nd, La, and Pr), the strontium-doped R 1 – x Sr x NiO 2 thin films show superconductivity with the critical temperature T c of 9–15 K at x = 0.2, whose origin of superconductivity deserves further investigation. Based on first-principles calculations, we study the electronic structure, lattice dynamics, and electron–phonon coupling (EPC) of the undoped and doped RNiO2 (R = Nd, La, and Pr) at the experimental doping level. Our results show that the EPC-derived T c’s are all about 0 K in the undoped and doped RNiO2. The electron–phonon coupling strength is too small to account for the observed superconductivity. We hence propose that the electron–phonon interaction can not be the exclusive origin of the superconductivity in RNiO2 (R = Nd, La, and Pr).